If f(x) = ln 4x, what is the value of f^-1(6). (The f raises to the -1 is the inverse function of f(x).

The answer is 100.86.

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- Sep 19th 2011, 05:29 PMbenny92000Inverse function
If f(x) = ln 4x, what is the value of f^-1(6). (The f raises to the -1 is the inverse function of f(x).

The answer is 100.86. - Sep 19th 2011, 05:38 PMAckbeetRe: Inverse function
So, let y = ln(4x). How, in general, do you invert functions?

- Sep 19th 2011, 06:09 PMPupilRe: Inverse function
The natural log (ln) has a base e, so another way of rewriting f(x) = ln 4x or y = ln 4x:

$\displaystyle e^{y} = 4x$

$\displaystyle \frac{e^{y}}{4} = x$

y = 6. Substituting it into this equation and solving for x will yield approximately 100.86.